Gas plasma panels having an inherent memory were originally disclosed in U.S. Pat. Nos. 3,499,167--Baker et al, and 3,559,190--Bitzer et al. These panels have several inherent advantages over the cathode ray tube display and are presently used commercially, principally as digitally addressable information display devices.
Basically, the panel consists of two glass plates with a gas mixture sealed between them. A plurality of X axis electrodes are deposited on the interior substrate of one plate and a plurality of Y axis electrodes are deposited on the interior of the other plate, thereby providing a plurality of intersecting X and Y electrodes. A voltage of between 200 and 250 volts is required to discharge the gas between intersecting electrodes to emit light at this point. A lesser alternating current voltage will sustain the gas in the light emitting state such that the gas will emit a pulse of light at each transition of the applied AC waveform. A precisely timed, shaped, and phased multiple alternating voltage waveform is required to control the generation, sustaining and erasure of light-emitting gas discharges at the selected locations on the plasma display panel.
Typically, in the prior art systems, a multiple level alternating voltage sustainer drive signal is applied to both the X and Y electrodes so as to present a composite sustainer waveform across the gas at each point or cell in the display panel where the X and Y electrodes intercept. As a result, each of the X and Y electrodes are required to be driven by one of the two separate complex sustainer circuits typically operating at 90 volts. An improvement to this system was disclosed in a U.S. Pat. No. 4,180,762 issued Dec. 25, 1979 by Larry Francis Weber and assigned to Interstate Electronics Corporation. This application discloses a means by which a single sustainer circuit is connected to one axis only of the panel electrodes and accomplishes the sustaining function for all electrodes in the panel.
A further disadvantage of the prior art systems is that they typically require at least seven different voltage levels to be supplied from the power supplies. These various voltage levels are required in order for the circuitry to generate the particular voltage waveforms required to control the generation, sustaining and erasure of light-emitting gas discharges at the selected locations on the plasma display panel. The power dissipated in generating these seven supply voltages, some of which must be adjustable, causes difficulties in packaging and cooling the display.
In addition to power dissipation problems associated with the drive systems, the amount of discrete component circuitry in the power supply and complex sustain voltage generator make these systems costly to produce and test.